File not recognized in objdump!!

File not recognized in objdump!!

[Aashish Gupta]

Hi..

I am trying to modify objdump to dump object file information for a
ELF64 file but on a different
kernel but its giving an error saying file format not recognized.

> [root@localhost binutils]# ./objdump -s /root/Desktop/testcase/test.o
> ./objdump: /root/Desktop/testcase/test.o: File format not recognized

Which part of the code should I look for in order to get through this error?

Thanks!!!


-- 
Regards,
Aashish Gupta.


---------------------------------------------------
Live life as  you have no tomorrow, dream as you have eternity..!!

File not recognized in objdump!!

[Aashish Gupta]

Hi..

I am trying to modify objdump to dump object file information for a
ELF64 file but on a different
kernel but its giving an error saying file format not recognized.

> [root@localhost binutils]# ./objdump -s /root/Desktop/testcase/test.o
> ./objdump: /root/Desktop/testcase/test.o: File format not recognized

Which part of the code should I look for in order to get through this error?

Thanks!!!


-- 
Regards,
Aashish Gupta.


---------------------------------------------------
Live life as  you have no tomorrow, dream as you have eternity..!!

Re: File not recognized in objdump!!

[Mike Frysinger]

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On Monday 26 March 2007, Aashish Gupta wrote:
> I am trying to modify objdump to dump object file information for a
> ELF64 file but on a different
> kernel but its giving an error saying file format not recognized.
>
> > [root@localhost binutils]# ./objdump -s /root/Desktop/testcase/test.o
> > ./objdump: /root/Desktop/testcase/test.o: File format not recognized
>
> Which part of the code should I look for in order to get through this
> error?

probably none ... build up a binutils for a target that supports the ELF 
format you're trying to analyze and/or build up binutils 
with --enable-targets=all
-mike

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Re: File not recognized in objdump!!

[Aashish Gupta]

Mike.. we have done a configure with the --target option which
recognozes the ELF64 file format and used the ia64 architecture.. Then
did a build which was neat worked without any errors./warnings..

So why is this error coming?

On 3/26/07, Mike Frysinger <vapier@gentoo.org> wrote:
> On Monday 26 March 2007, Aashish Gupta wrote:
> > I am trying to modify objdump to dump object file information for a
> > ELF64 file but on a different
> > kernel but its giving an error saying file format not recognized.
> >
> > > [root@localhost binutils]# ./objdump -s /root/Desktop/testcase/test.o
> > > ./objdump: /root/Desktop/testcase/test.o: File format not recognized
> >
> > Which part of the code should I look for in order to get through this
> > error?
>
> probably none ... build up a binutils for a target that supports the ELF
> format you're trying to analyze and/or build up binutils
> with --enable-targets=all
> -mike
>
>


-- 
Regards,
Aashish Gupta.


---------------------------------------------------
Live life as  you have no tomorrow, dream as you have eternity..!!

Re: File not recognized in objdump!!

[H. J. Lu]

On Mon, Mar 26, 2007 at 11:15:21AM +0530, Aashish Gupta wrote:
> Mike.. we have done a configure with the --target option which
> recognozes the ELF64 file format and used the ia64 architecture.. Then
> did a build which was neat worked without any errors./warnings..
> 
> So why is this error coming?
> 

What does "readelf -a" say?


H.J.

Re: File not recognized in objdump!!

[Jim Wilson]

On Mon, 2007-03-26 at 10:44 +0530, Aashish Gupta wrote:
> I am trying to modify objdump to dump object file information for a
> ELF64 file but on a different
> kernel but its giving an error saying file format not recognized.

Trying the command
  grep "File format not recognized"
we find it is defined in bfd.c.  Looking at this file, we see that this
is in an error, and an enum defined nearby shows that the array index is
bfd_error_file_not_recognized.  So now grepping for that enum, we find
that there are two bfd_set_error calls in the file format.c that use it.
Both calls are in the function bfd_check_format_matches.  Run objdump
under gdb, put a breakpoint here, and step through the code to see what
it is doing.
-- 
Jim Wilson, GNU Tools Support, http://www.specifix.com

Re: File not recognized in objdump!!

[Jim Wilson]

On Mon, 2007-03-26 at 10:44 +0530, Aashish Gupta wrote:
> I am trying to modify objdump to dump object file information for a
> ELF64 file but on a different
> kernel but its giving an error saying file format not recognized.

Trying the command
  grep "File format not recognized"
we find it is defined in bfd.c.  Looking at this file, we see that this
is in an error, and an enum defined nearby shows that the array index is
bfd_error_file_not_recognized.  So now grepping for that enum, we find
that there are two bfd_set_error calls in the file format.c that use it.
Both calls are in the function bfd_check_format_matches.  Run objdump
under gdb, put a breakpoint here, and step through the code to see what
it is doing.
-- 
Jim Wilson, GNU Tools Support, http://www.specifix.com

Re: File not recognized in objdump!!

[Jim Wilson]

FYI sources.redhat.com and sourceware.org are the same machine.  Please
don't send the same message to both addresses.  That results in everyone
receiving it twice.  The sourceware.org name is the preferred one.  And
I fixed the cc line so I'm not making the same mistake again.
-- 
Jim Wilson, GNU Tools Support, http://www.specifix.com

Re: File not recognized in objdump!!

[Aashish Gupta]

Jim,
I already stepped through the fucntion "bfd_check_format_matches" and
figured out that its not recognizing the target format ... The error
looks something like this..


(gdb) run objdump
Starting program: /root/Desktop/binutils1/gas/as-new objdump

Breakpoint 6, as_perror (gripe=0x80d7638 "Selected target format '%s' unknown",
    filename=0x80db2be "elf64-ia64-little") at messages.c:124

((Our target is elf64-ia64-big though ..?? and have made modification
accordingly..))
124     {
(gdb) break bfd_check_format_matches
Breakpoint 9 at 0x8088099: file format.c, line 118.
(gdb) n
126       int saved_errno = errno;
(gdb) n
128       as_show_where ();
(gdb) n
Assembler messages:
129       fprintf (stderr, gripe, filename);
(gdb) n
Selected target format 'elf64-ia64-little' unknown130     errno = saved_errno;
(gdb) n
131       errtxt = bfd_errmsg (bfd_get_error ());
(gdb) n
132       fprintf (stderr, ": %s\n", errtxt);
(gdb) n
: Invalid bfd target
133       errno = 0;
(gdb) n
135     }
(gdb) n
134       bfd_set_error (bfd_error_no_error);
(gdb)
135     }
(gdb) n
as_perror (gripe=0x80d4a34 "a.out", filename=0x0) at messages.c:134
134       bfd_set_error (bfd_error_no_error);


Thanks..

> On 3/27/07, Jim Wilson <wilson@specifix.com> wrote:
> >  On Mon, 2007-03-26 at 10:44 +0530, Aashish Gupta wrote:
> > > I am trying to modify objdump to dump object file information for a
> > > ELF64 file but on a different
> > > kernel but its giving an error saying file format not recognized.
> >
> > Trying the command
> >   grep "File format not recognized"
> > we find it is defined in bfd.c.  Looking at this file, we see that this
> > is in an error, and an enum defined nearby shows that the array index is
> > bfd_error_file_not_recognized.  So now grepping for that enum, we find
> > that there are two bfd_set_error calls in the file format.c that use it.
> > Both calls are in the function bfd_check_format_matches.  Run objdump
> > under gdb, put a breakpoint here, and step through the code to see what
> > it is doing.
> > --
> > Jim Wilson, GNU Tools Support, http://www.specifix.com
> >
> >
> >
>
>
>
>
> --
> Regards,
> Aashish Gupta.
>
>
> ---------------------------------------------------
> Live life as  you have no tomorrow, dream as you have eternity..!!



-- 
Regards,
Aashish Gupta.


---------------------------------------------------
Live life as  you have no tomorrow, dream as you have eternity..!!

Re: File not recognized in objdump!!

[Nick Clifton]

Hi Aashish,


> I am trying to modify objdump to dump object file information for a
> ELF64 file but on a different
> kernel but its giving an error saying file format not recognized.

Try looking at the source code for the function elfNN_ia64_object_p in 
bfd/elfxx-ia64.c.  This is probably where your object file should be 
recognised.  (Note, during the binutils building process the "NN" in 
elfNN_ia64_object_p is replaced with "64", hence when you are debugging 
objdump you should look for the function elf64_ia64_object_p).

Cheers
   Nick

Re: File not recognized in objdump!!

[Nick Clifton]

Hi Aashish,


> I am trying to modify objdump to dump object file information for a
> ELF64 file but on a different
> kernel but its giving an error saying file format not recognized.

Try looking at the source code for the function elfNN_ia64_object_p in 
bfd/elfxx-ia64.c.  This is probably where your object file should be 
recognised.  (Note, during the binutils building process the "NN" in 
elfNN_ia64_object_p is replaced with "64", hence when you are debugging 
objdump you should look for the function elf64_ia64_object_p).

Cheers
   Nick

Re: File not recognized in objdump!!

[Jim Wilson]

On Tue, 2007-03-27 at 12:54 +0530, Aashish Gupta wrote:
> (gdb) run objdump
> Starting program: /root/Desktop/binutils1/gas/as-new objdump
> Breakpoint 6, as_perror (gripe=0x80d7638 "Selected target format '%s' unknown",
>     filename=0x80db2be "elf64-ia64-little") at messages.c:124
> ((Our target is elf64-ia64-big though ..?? and have made modification
> accordingly..))
> 124     {
> (gdb) break bfd_check_format_matches
> Breakpoint 9 at 0x8088099: file format.c, line 118.
> (gdb) n
> 126       int saved_errno = errno;

There are a lot of problems with what you are doing here.

First of all, you are debugging the assembler, not objdump here.  See
the "starting program" line, and the fact that as_perror is an assembler
routine.  Also, you are running it incorrectly, as you passed the
objdump binary to it.  The assembler only accepts assembly source files
as input.  You need to be debugging the right program with the right
input.

You set the bfd_check_format_matches breakpoint after starting the
program, and then typed next, which is not going to work.  This will
leave you where you are already stopped, which is in the as_perror
function.  This routine just prints out the error message, which is far
too late to be useful.

You need to set the breakpoint first, and then run the program.  If you
debug the right program, and the right function, you will see that it
ends up calling the elf64_ia64_object_p function which Nick pointed you
at.

binutils is a large and complicated package.  You will need to spend a
lot more time learning how it works, and how to use basic tools like
gdb, if you wish to be successful modifying it.
-- 
Jim Wilson, GNU Tools Support, http://www.specifix.com